Voice activity detectors are known. Third Generation Partnership Project (3GPP) standard TS 26.094 “Mandatory Speech Codec speech processing functions; AMR speech codec; Voice Activity Detector (VAD)” describes a solution for voice activity detection in the context of GSM (Global System for Mobile Systems) and WCDMA (Wide-Band Code Division Multiple Access) telecommunication systems. In this solution an audio signal and its noise component is estimated in different frequency bands and a voice activity decision is made based on that. This solution does not provide any multi-microphone operation but speech signal from one microphone is used.